This invention relates to commercial truck trailers and the like, and more particularly to such trailers that incorporate steerable front wheel assemblies mounted on the trailer frame by a turntable apparatus.
In order to better distinguish the particular environment involved in the present invention, conventional commercial truck trailers commonly seen on highways may be divided into two broad categories: Those having wheel-bearing rear axles and a front fifth wheel-type hitch arrangement, and those trailers which are supported both in the front and rear by their own wheel-bearing axle assemblies. The former category usually finds the trailer connected directly to the tractor rig, or alternatively, the front end of the trailer is supported on a wheeled dolly which itself mounts the corresponding "horse-shoe" component of a fifth wheel hitch. In both of these cases, steering of the trailer is accomplished by the normal rotational pivoting of the fifth wheel components relative to each other as is well understood in the art.
It is the second category identified above that relates to the present invention. In these trailer constructions, most often seen in very heavy tanker trailers, platform flatbed trailers, log hauling trailers, and other types of trailers, single and dual axle assemblies are mounted on the trailer, both front and rear, making the trailer entirely self-supported on the road. Typically, the rear axles, of course, are mounted in a fixed, straight-forward orientation. However, even a novice will recognize that if the front wheels of the trailer were similarly fixed in a straightforward orientation, the trailer would not be steerable, and would only be able to go straight-forward unless the front end of the trailer were literally dragged around a turn by the pull of the preceeding vehicle or trainer. Accordingly, these trailers have included separate carriage assemblies that mount the front axles and suspension, the carriage mounted to the trailer frame through a very heavy-duty turntable which permits rotation of the front carriage relative to the trailer frame.
These turntable assemblies are known in the art, as illustrated in U.S. Pat. Nos. 2,588,078 and 3,096,099 and shown in a 1983 sales publication by Fab Tek Incorporated. These constructions, which are subject to extremely heavy, vigorous and constant use, have necessarily involved very substantial, structurally complex, cast steel assemblies that require extensive machining and fabrication in manufacture and assembly, and consequently are difficult to maintain and repair. As a result, manufacturing costs are high, and high upkeep time and costs often promote lack of proper maintenance and repair.